It's more pricing. In Canada that psu is about 20-30 euro more, not 5. So for such a minor cost difference it is worth it. But if you were going to be spending a lot more then it wouldn't be worth it. A 520w Seasonic will be good for any single gpu for a while. Power consumption has been going down, not up.
Oh and Haswell Ready is marketing bullshit. Ignore it.
Oh and Haswell Ready is marketing bullshit. Ignore it.